Possible Clues:

• Feature of a pipe organ
• Pipe organ mechanism
• Engineers by depots supply set of pipes
• Pipe organist's selection
• Sort of postered set of organ pipes
• Set of organ pipes; do preset (anag.)
• Studies audibly highest part of organ
• A lot of grass - drug put back in pipes
• On the organ it's the turn of one who takes a shot at 12 across